Fear of Loss is best motivator - Why isn't it working as millions lose their life to obesity

Psychologically, we fear losing something we have much more than we enjoy possible gains.  Psychologists claim this bias is proven across all ages, gender and ethnicity.  We value the loss more than the gain, by 2-3 times.  This law of motivation got me thinking about why isn't it working when we look at the quality and potential of our lives.  Look around at the obesity increases among our community, they are losing their lives.  They had a life, sex, movement without pain, no medication, no sleep apnea, and they have traded all of this for poor eating and lifestyle habits.  I am confused by how the Fear of Loss is not making a stronger impact on the choices we are making since psychology says it should.